A neurotransmitter receptor can be paired directly with an ion channel, but most send signals indirectly though [[guanyl nucleotide-binding proteins]] or [[G proteins]] <ref>{{cite book|last=Levitan|first=Irwin B.|coauthors=Leonard K. Kaczmarek|title=The Neuron|publisher=Oxford University Press|date=2002|edition=Third pg. 285}}</ref> Interactions between neurotransmitters and neurotransmitter receptors are involved in a wide range of differing reactions from the cell receiving the signal, triggering anything from activation to [[inhibition]].

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A neurotransmitter receptor can be paired directly with an ion channel, but most send signals indirectly though [[guanyl nucleotide-binding proteins]] or [[G proteins]] <ref>{{cite book|last=Levitan|first=Irwin B.|coauthors=Leonard K. Kaczmarek|title=The Neuron|publisher=Oxford University Press|date=2002|edition=Third pg. 285}}</ref> Interactions between neurotransmitters and neurotransmitter receptors are involved in a wide range of differing reactions from the cell receiving the signal, triggering anything from activation to [[inhibition]].

A neurotransmitter receptor is a membrane receptor protein that interacts with neurotransmitters and mediate the flow of sinals through a neural network. A membrane protein interacts with the lipid bilayer that encloses the cell [1] and a membrane receptor protein interacts with a chemical in the cells external environment, which binds to the cell [2] . Membrane receptor proteins are particularly important in neuronal and glial (involved in neuronal transmission, but not technically neurons) cells, because they allow cells to communicate with one another through chemical signals. Neurotransmitter receptors send and receive signals that trigger an electrical signal that runs along the neuron and can be passed along a neural network, by regulating the activity of ion channels. [3]
It is important to appreciate that these receptors are not static structures but rather protein molecules produced within the neuron and they become temporarily embedded in the cell walls so that a portion of the molecule is exposed and acts as a binding site so that messenger molecules can attach themselves and so activate the receptor [citation needed]. The life cycle of individual receptors is only about 12-24 hours, after which they are deactivated through use or reabsorbed into the cell[citation needed]

Most nerve cells have between 2000 and 3000 receptors on their surface[citation needed]}. Even where cells are specialized for one type of receptor molecule they usually are sensitive to other neurotransmitters. So for example a serotonin cell may have dopamine receptors as well as opiate receptors etc. The absolute number of receptors and the ratio of inhibiory to excitory receptors determines the reaction of the cell.

A neurotransmitter receptor can be paired directly with an ion channel, but most send signals indirectly though guanyl nucleotide-binding proteins or G proteins[4] Interactions between neurotransmitters and neurotransmitter receptors are involved in a wide range of differing reactions from the cell receiving the signal, triggering anything from activation to inhibition.

One additional characteristic of neurotransmitter receptors is that they are subject to ligand-induced desensitization: That is, they can become unresponsive upon prolonged exposure to their neurotransmitter. Neurotransmitter receptors are present on both postsynaptic neurons and presynaptic neurons with the former being used to receive neurotransmitters and the latter for the purpose of preventing further release of a given neurotransmitter[1]. In addition to being found in neuron cells, neurotransmitter receptors are also found in various immune and muscle tissues[2]. Many neurotransmitter receptors are categorized as a serpentine receptor or G protein-coupled receptor because they span the cell membrane not once, but seven times. Neurotransmitter receptors are known to become unresponsive to the type of neurotransmitter they receive when exposed for extended periods of time. This phenomenon is known as ligand-induced desensitization[3] or downregulation.